1. Field of the Invention
The present invention generally relates to an oscillation circuit including a MOSFET driven by an oscillation output.
2. Description of the Related Art
It is preferable for an oscillation circuit to output an oscillation waveform having a predetermined oscillating frequency f irrespective of existence of a load or a load current. Therefore, an output stage circuit for ensuring a capability of driving the load and relaxing an influence of the load is necessary.
FIG. 1 illustrates an exemplary output stage circuit 50 of a conventional oscillation circuit 50. The output stage circuit includes a CMOS inverter with which an oscillation output from the oscillation output generation circuit 80 is input in transistors MH and ML. The output waveform from the CMOS inverter is output to a load 60 as an oscillation waveform having a predetermined frequency f via an output terminal 63. The electric current flowing through the load 60 is supplied from a constant voltage source 71.
However, if the impedance of the load outwardly connected to the oscillation circuit is changed, a capability of driving the load cannot be adjusted so as to be suitable for the changed impedance of the load with the conventional technique. Therefore, if plural variations exist in the load outwardly connected to the oscillation circuit, the oscillation circuit can be hardly adjusted in response to the variations.    [Patent Document 1] Japanese Laid-open Patent Publication No. 2006-311379